How Many Porta Potties Do You Need?

Two different questions wear the same words. For an event you are guessing at comfort; for a job site you are meeting a federal minimum. The numbers are not close to each other, so start by deciding which one you are answering.

Events

The working figure across the industry is one unit per 50 guests for an event up to four hours. It comes from ANSI/PSAI Z4.3, the standard covering temporary event sanitation, and every calculator you will find online is a restatement of it.

Three things move it. Alcohol pushes usage up 15 to 20%, because people drink more and stay longer. Duration compounds — the same crowd over eight hours needs meaningfully more capacity than over four. And a crowd that skews female needs more units, which is why large events add urinal banks to take pressure off the restrooms.

Job sites

Here the number is law. 29 CFR 1926.51(c) sets one toilet for up to 20 workers, then one toilet seat and one urinal per 40 workers, and per 50 above 200 workers. That is a floor, not a target — a crew losing ten minutes each way walking to a single unit costs more in time than the second unit costs to rent.

ADA units

Any event open to the public should have at least one wheelchair-accessible unit, and the common industry guidance is 5% of your total with a minimum of one. They also run out first on a busy weekend, so book that one before the standard units rather than after.

Hand-wash stations

Roughly one per four units, and non-negotiable where food is served. They are ordered separately from the restrooms, which is why they are the thing most often missing from a quote. Ask explicitly.

Work it out for your numbers →

Figures on this page come from the Porta Potty Finder, last checked 2026-08-18. How the data is collected.